Flow controlling apparatus for power steering

ABSTRACT

It is one object of the present invention to provide a flow controlling apparatus for a power steering preventing a driver from feeling incompatibility. The flow controlling apparatus for the power steering comprises; a variable throttle mechanism installed in the pump to change fluid of discharged oil from the pump to a hydraulic device; a linear solenoid mechanism controlling the variable throttle mechanism by said predetermined energized current; a spool feeding back the exceeding fluid of said discharged oil to a bypass passage of the pump in accordance with differential pressure between upstream and downstream at the variable throttle mechanism when the exceeding fluid exceeds a predetermined value; and control means controlling the energized current to change transition process in accordance with a steering angular velocity of the steering wheel.

INCORPORATION BY REFERENCE

The present application claims priority under 35 U.S.C. §119 to JapanesePatent Applications No. 2003-177711, filed on Jun. 23, 2003. The contentof this application is incorporated herein by reference in theirentirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a flow controlling apparatus for apower steering controlling electrically in constant fluid of operationaloil from oil pump to a hydraulic device to assist a steering wheel of avehicle by hydraulic power.

2. Description of the Related Art

It is well known for a flow controlling apparatus for a power steeringto keep in a predetermined value the discharged fluid of operational oilto a hydraulic device in accordance with such a vehicle speed or asteering angle of a steering wheel, for example as shown in Japaneselaid-open patent publication No. 2001-163233. In this related art, thedischarged fluid is controlled by a variable valve equipped in an outletof the flow controlling apparatus by energizing a solenoid. The solenoidis controlled by an electric signal relating to the vehicle speed or thesteering angle through control means of a micro computer. The solenoidis energized in accordance with the electric signal to operate thevariable valve in order to control the amount of fluid to the hydraulicdevice of the power steering.

In the well known power steering, since the solenoid is energized inaccordance with the electric signal relating to the vehicle speed or thesteering angle of the steering wheel to operate the variable valve inorder to control the amount of fluid to the hydraulic device of thepower steering, it is best way for energy saving that the amount ofdischarged fluid is zero where the steering is not operated by judgingthe steering angle. However, where the amount of discharged fluid iszero, it has a possibility to happen that there occurs seizure in thehydraulic device or unsteady driving based on disturbance such akick-back and so on in straight run. Further, it needs time at a rapidsteering for the discharged fluid to increase to a suitable amount,causing late response of power assistance by the hydraulic device.Because of this reason, the well known flow controlling apparatus keepsminimum fluid discharged to the hydraulic device of the power steeringas standby fluid for waiting to assist the steering wheel. Therefore, itis easy to reach to the predetermines amount of fluid from the standbyfluid even though at rapid steering. The well known electricallycontrolled flow controlling device controls in only one or single way oftransition from standby fluid Qs to suitable amount of fluid (Qa) neededfor assisting by the hydraulic device, that is to say time constantrelating to stand up from Qs to Qa is only one or single, as shown inFIG. 1. Therefore, where the time constant is set for the rapid steeringin the control mans, the assisting force is suddenly and unexpectedlyrisen at a slow steering thereby to make the driver feelincompatibility.

SUMMARY OF THE INVENTION

In view of the previously mentioned circumstances, it is an object ofthe present invention to provide a flow controlling apparatus for apower steering preventing a driver from feeling incompatibility.

In order to achieve the above and other objects, the present inventionprovides the flow controlling apparatus for tile power steering mainlycomprising control means to change transition in accordance with asteering angular velocity of the steering wheel. The transition is astatus from standby fluid, for waiting to assist the steering wheel, toassisting fluid to assist the steering wheel by hydraulic power. By thisconstruction of the present invention, the transition process from thestandby fluid to the assisting fluid is easily changed so that it doesnot make the driver feel incompatibility and therefore do perform togive the assisting force effectively.

Second aspect of the flow controlling apparatus for the power steeringof the present invention is that said control means control in such away that the transition process is rapid when the steering angularvelocity is large, and the transition process is slow when the steeringangular velocity is small. More particularly, another aspect of the flowcontrolling apparatus for the power steering is that said control meansset time constant in small value so that the transition process is rapidwhen the steering angular velocity is large, and set time constant inlarge value so that the transition process is slow when the steeringangular velocity is small. By this construction of the presentinvention, at the rapid steering the transition from standby fluid toassisting fluid is performed swiftly so that the suitable powerassistance is done. Thereby, the driver does not feel the caught statusbased on rapid increasing of torque response force, and the smooth powerassistance is performed. At the slow steering the transition fromstandby fluid to assisting fluid is performed slowly so that theassisting force is not applied rapidly. Thereby, the driver does notfeel incompatibility.

BRIEF DESCRIPTION OF THE DRAWINGS

Various other objects, features and many of the attendant advantages ofthe present invention will be readily appreciated as the same becomesbetter understood by reference to the following detailed description ofthe preferred embodiments when considered in connection with theaccompanying drawings, in which:

FIG. 1 is a graph showing operational situation in a related art;

FIG. 2 is an explanatory drawing of a whole construction of oneembodiment of the present invention;

FIG. 3 is a vertical sectional view of a whole construction of avariable throttle mechanism and a solenoid mechanism consisting of mainportions of one embodiment of the present invention; and

FIG. 4 is a graph showing operational situation in one embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A preferred embodiment of a flow controlling apparatus for a powersteering according to the present invention will be described referringto FIG. 2 to FIG. 4. In FIG. 2, the power steering includes a hydraulicdevice 9 and the hydraulic device 9 receives pressurized dischargedoperating oil from a pump 1 through the flow controlling apparatus inorder to assist a rotation of a steering wheel of a vehicle by hydraulicpower. The flow controlling apparatus controls discharged oil suitablyto feed to the hydraulic device 9 and is installed in an outlet portionof the pump 1 through which the pump 1 outputs the discharged oil. Theflow controlling apparatus comprises mainly a variable throttlemechanism 12, a spool 15 and control means 5. The variable throttlemechanism 12 is controlled by a linear solenoid mechanism 2 incorrespondence to a predetermined value of an energized current. When avolume of fluid of discharged oil from the pump 1 to the hydraulicdevice 9 is exceeded over a predetermined value, the spool 15 feeds backthe exceeded discharged oil to a bypass passage 17 in accordance withdifferential pressure in between upper stream and lower stream of thevariable throttle mechanism 12. The bypass passage 17 is provided toconnect to an inlet port of the pump 1. Control means 5 controlenergized current to the linear solenoid mechanism 2 suitably incorrespondence with such running state of the vehicle or steering stateof the steering wheel.

The spool 15, the variable throttle mechanism 12 and other componentsare installed in a housing of the pump 1 as shown in FIG. 3. The spool15 is slidably mounted in the housing 19 in order to feed mainlydischarged oil from the pump 1 through an introducing chamber 11, formedin a side of the head of the spool 15, to the hydraulic device 9 andfeed back the exceeded discharged oil from the pump 1 to the bypasspassage 17. The linear solenoid mechanism 2 is mounted on a union 16 atone end of the housing 19 having the bypass passage 17 and so on.Mounted in the union 16 is the variable throttle mechanism 12, theopening degree of which is controlled by the linear solenoid mechanism2. Around the variable throttle mechanism 12 there is an outlet 25,through which controlled discharged oil is discharged to the hydraulicdevice 9 composing the power steering. The spool 15 is operatedaccording to the differential pressure in between the upper and lowerstream of the variable throttle mechanism 12 in order that exceededdischarged oil is fed back to the bypass passage 17.

The linear solenoid mechanism 2 comprises a valve body 22 forming thevariable throttle mechanism 12; a movable armature core 21 connected tothe valve body 22; coils 23 mounted outward the movable armature core 21to move thereof slidably; and an un-illustrated spring to chargeresistance to the movable armature core 21 in order to hold thereof indesired position of the movable armature core 21 in accordance with theamount of energized current to the coils 23. Control means 5 inputs theenergized current to coils 23 composing the solenoid mechanism 2 inorder to control operations of the linear solenoid mechanism 2, as shownin FIG. 2. Into control means 5 are fed various signals from such avehicle speed sensor, a steering angle sensor of the steering wheel, asteering angular velocity sensor of the steering wheel to performpredetermined calculation. The control means 5 is constructed by a microcomputer with a micro processor (MPU), performing predeterminedcalculation based on read only memory (ROM) data input previously. Afterreceiving and calculating input signals, control means 5 orderspredetermined energized current to the linear solenoid mechanism 2.

The operation of the embodiment of the present invention will bedescribed hereinafter referred to FIG. 2 to FIG. 4. After the pump 1 isoperated to start, discharged oil from the pump 1 is introduced into theintroducing chamber 11 and thereafter fed into the hydraulic device 9constructed the power steering via the variable throttle mechanism 12controlled by the linear solenoid mechanism 2 and the outlet 25, therebyassisting the steering wheel of the vehicle by the hydraulic power. Atthat time, where turning velocity of the pump rotor increased todischarge the discharged oil exceeding over the predetermined value, theexceeded discharged oil is fed back to the bypass passage 17 shown inFIG. 3. Therefore, fluid discharged from the outlet 25 is maintained inconstant. This means the stage of constant fluid control for the pump.The fluid in constant control stage is determined by the predeterminedcalculation by control means 5 based on information from various sensors7 including the vehicle speed sensor, etc.

In addition to this basic operation of the embodiment, it controls nextoperation.

It is well known in the power steering that the electrically controlledflow controlling apparatus controls fluid as previously described inFIG. 1. Namely, the well known electrically controlled flow controllingdevice controls in such a way that predetermined standby fluid Qs is fedfrom a flow controlling device for waiting to assist the steering wheelin order to prevent seizure in a hydraulic device, unsteady driving instraight run, late response of power assistance by the hydraulic device,and so on. This means the stage of standby fluid control for a pump. Inthis standby stage, after a steering wheel is operated, a linearsolenoid mechanism is operated to keep suitable amount of fluid (Qa)needed for assistance by the hydraulic device on the basis of commandsfrom control means, thereby discharging the suitable amount of fluid tothe hydraulic device constructing a power steering for assisting thesteering wheel by hydraulic fluid. In the related art of the flowcontrolling apparatus of the well known power steering, the transitionprocess from the standby fluid (Qs) to assisting fluid (Qa) is constantor stable, that is to say time constant relating to stand up from Qs toQa is only one or single. Therefore, where the time constant is set asrelatively small value for a rapid steering in the control mans, theassisting force is suddenly and unexpectedly risen at a slow steeringthereby to make the driver feel incompatibility. On the contrary, wherethe time constant is set as relatively large value for a slow steeringin the control means, the suitable assisting force is not appliedimmediately at the rapid steering thereby to make the driver feel theshocked steering response. These phenomena are so-called caught statusbased on late response in power assistance. The caught status make thedriver feel incompatibility.

In order to solve the problem in the related art, in the embodiment ofthe present invention the control means 5 changes said time constant inaccordance with the steering status of the steering wheel, in detail inaccordance with the steering angular velocity of the steering wheel. Theembodiment of the present invention changes the value of the transitionfrom the standby fluid (Qs) to assisting fluid (Qa), that is to say toset said time constant as the small value at the large steering angularvelocity, that is the rapid steering, as shown by a dotted line in FIG.4 and to set said time constant as the large value at the small steeringangular velocity, that is the slow steering, as shown by a solid line inFIG. 4. By these setting of the value of time constant, at the rapidsteering the transition from standby fluid to assisting fluid isperformed swiftly so that the suitable power assistance is done.Thereby, the driver does not feel the caught status based on rapidincreasing of torque response force, and the smooth power assistance isperformed. At the slow steering the transition from standby fluid toassisting fluid is performed slowly so that the assisting force is notapplied rapidly. Thereby, the driver does not feel incompatibility. Indetail operation, the control means 5 control the energized current as0.2 A (ampere) to the coils 23 thereby to move the movable armature core21 so that relatively small amount of the opening degree of the variablethrottle mechanism 12 is kept in order to keep the discharged standbyfluid Qs from the outlet 25 in 2 l/min. for standby fluid, for waitingto assist the steering wheel in order to prevent seizure in thehydraulic device 9, unsteady driving in straight run, late response ofpower assistance by the hydraulic device 9, and so on. And the controlmeans 5 control the energized current as 0.8 A (ampere) to the coils 23thereby to move the movable armature core 21 so that relatively largeamount of the opening degree of the variable throttle mechanism 12 iskept in order to keep the discharged assisting fluid Qa from the outlet25 in 8 l/min. for steering fluid, for assisting the rotation of thesteering wheel by hydraulic power. In the transition process from Qs toQa, the control means 5 change the energized current from 0.2 A to 0.8 Acontinuously with the above-described predetermined time constant whichis unchangeable during this identified transition process. FIG. 3 showsonly two types of transition for easy understanding, however the controlmeans 5 change continuously the value of time constant according to thevariation of the steering angular velocity.

While the invention has been described in detail with reference to thepreferred embodiment, it will be, apparent to those skilled in the artthat the invention is not limited to the present embodiment, and thatthe invention may be realized in various other embodiments within thescope of the claims. For example, in the above-mentioned embodiment ofthe present invention, the time constant is changed by the control means5 according to the steering angular velocity, however, it may be changedin accordance with the vehicle speed or the steering angle.

Furthermore, the technological components described in thisspecification and illustrated in the drawings can demonstrate theirtechnological usefulness independently through various othercombinations which are not limited to the combinations described in theclaims made at the time of application. Moreover, the art described inthis specification and illustrated in the drawings can simultaneouslyachieve a plurality of objectives, and is technologically useful byvirtue of realizing any one of these objectives.

1. A flow controlling apparatus for a power steering comprising: a pump;a hydraulic device constructing said power steering and receivingdischarged oil from said pump to assist a steering wheel by hydraulicpower; a variable throttle mechanism installed in said pump to changefluid of said discharged oil from said pump to said hydraulic device; alinear solenoid mechanism controlling said variable throttle mechanismby said predetermined energized current; a spool feeding back theexceeding fluid of said discharged oil to a bypass passage of said pumpin accordance with differential pressure between upstream and downstreamat said variable throttle mechanism when said exceeding fluid exceeds apredetermined value; and control means controlling said energizedcurrent to change transition process in accordance with a steeringangular velocity of said steering wheel, said power steering is in astandby stage by said standby fluid for waiting to assist said steeringwheel and in assisting stage by said assisting fluid for assisting saidsteering wheel by said hydraulic power, said transition process istransited from standby fluid to assisting fluid.
 2. A flow controllingapparatus for a power steering according to claim 1, wherein saidcontrol means control in such a way that said transition process israpid when said steering angular velocity is large, and said transitionprocess is slow when said steering angular velocity is small.
 3. A flowcontrolling apparatus for a power steering according to claim 2, whereinsaid control means set time constant in small value so that saidtransition process is rapid when said steering angular velocity islarge, and set time constant in large value so that said transitionprocess is slow when said steering angular velocity is small.
 4. A flowcontrolling apparatus for a power steering comprising: a pump; ahydraulic device constructing said power steering and receivingdischarged oil from said pump to assist a steering wheel by hydraulicpower; a variable throttle mechanism installed in said pump to changefluid of said discharged oil from said pump to said hydraulic device; alinear solenoid mechanism controlling said variable throttle mechanismby said predetermined energized current; a spool feeding back theexceeding fluid of said discharged oil to a bypass passage of said pumpin accordance with differential pressure between upstream and downstreamat said variable throttle mechanism when said exceeding fluid exceeds apredetermined value; and control means controlling said energizedcurrent to change transition process in accordance with a vehicle speedof said steering wheel, said power steering is in a standby stage bysaid standby fluid for waiting to assist said steering wheel and inassisting stage by said assisting fluid for assisting said steeringwheel by said hydraulic power, said transition process is transited fromstandby fluid to assisting fluid.
 5. A flow controlling apparatus for apower steering according to claim 4, wherein said control means controlin such a way that said transition process is rapid when said steeringangular velocity is large, and said transition process is slow when saidsteering angular velocity is small.
 6. A flow controlling apparatus fora power steering according to claim 5, wherein said control means settime constant in small value so that said transition process is rapidwhen said steering angular velocity is large, and set time constant inlarge value so that said transition process is slow when said steeringangular velocity is small.
 7. A flow controlling apparatus for a powersteering comprising: a pump; a hydraulic device constructing said powersteering and receiving discharged oil from said pump to assist asteering wheel by hydraulic power; a variable throttle mechanisminstalled in said pump to change fluid of said discharged oil from saidpump to said hydraulic device; a linear solenoid mechanism controllingsaid variable throttle mechanism by said predetermined energizedcurrent; a spool feeding back the exceeding fluid of said discharged oilto a bypass passage of said pump in accordance with differentialpressure between upstream and downstream at said variable throttlemechanism when said exceeding fluid exceeds a predetermined value; andcontrol means controlling said energized current to change transitionprocess in accordance with a steering angle of said steering wheel, saidpower steering is in a standby stage by said standby fluid for waitingto assist said steering wheel and in assisting stage by said assistingfluid for assisting said steering wheel by said hydraulic power, saidtransition process is transited from standby fluid to assisting fluid.8. A flow controlling apparatus for a power steering according to claim7, wherein said control means control in such a way that said transitionprocess is rapid when said steering angular velocity is large, and saidtransition process is slow when said steering angular velocity is small.9. A flow controlling apparatus for a power steering according to claim8, wherein said control means set time constant in small value so thatsaid transition process is rapid when said steering angular velocity islarge, and set time constant in large value so that said transitionprocess is slow when said steering angular velocity is small.